>From 0b36864d4100ecbdcaa2fc2d1927c9e270f1b629 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <[email protected]> Date: Wed, 17 Feb 2016 16:37:59 +0900 Subject: [PATCH 6/6] mm,oom: wait for OOM victims when using oom_kill_allocating_task == 1
Currently, out_of_memory() does not wait for existing TIF_MEMDIE threads if /proc/sys/vm/oom_kill_allocating_task is set to 1. This can result in killing more OOM victims than needed. We can wait for the OOM reaper to reap memory used by existing TIF_MEMDIE threads if possible. If the OOM reaper is not available, the system will be kept OOM stalled until an OOM-unkillable thread does a GFP_FS allocation request and calls oom_kill_allocating_task == 0 path. This patch changes oom_kill_allocating_task == 1 case to call select_bad_process() in order to wait for existing TIF_MEMDIE threads. Since "mm,oom: exclude TIF_MEMDIE processes from candidates.", "mm,oom: don't abort on exiting processes when selecting a victim.", "mm,oom: exclude oom_task_origin processes if they are OOM victims.", "mm,oom: exclude oom_task_origin processes if they are OOM-unkillable." and "mm,oom: Re-enable OOM killer using timers." made sure that we never wait for TIF_MEMDIE threads forever, waiting for TIF_MEMDIE threads for oom_kill_allocating_task == 1 does not cause OOM livelock problem. After this patch, we can safely merge the OOM reaper in the simplest form, without worrying about corner cases. Signed-off-by: Tetsuo Handa <[email protected]> --- mm/oom_kill.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index fba2c62..9cd1cd1 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -737,15 +737,6 @@ bool out_of_memory(struct oom_control *oc) oc->nodemask = NULL; check_panic_on_oom(oc, constraint, NULL); - if (sysctl_oom_kill_allocating_task && current->mm && - !oom_unkillable_task(current, NULL, oc->nodemask) && - current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { - get_task_struct(current); - oom_kill_process(oc, current, 0, totalpages, NULL, - "Out of memory (oom_kill_allocating_task)"); - return true; - } - p = select_bad_process(oc, &points, totalpages); /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p && !is_sysrq_oom(oc)) { @@ -753,8 +744,18 @@ bool out_of_memory(struct oom_control *oc) panic("Out of memory and no killable processes...\n"); } if (p && p != (void *)-1UL) { - oom_kill_process(oc, p, points, totalpages, NULL, - "Out of memory"); + const char *message = "Out of memory"; + + if (sysctl_oom_kill_allocating_task && current->mm && + !oom_unkillable_task(current, NULL, oc->nodemask) && + current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { + put_task_struct(p); + p = current; + get_task_struct(p); + message = "Out of memory (oom_kill_allocating_task)"; + points = 0; + } + oom_kill_process(oc, p, points, totalpages, NULL, message); /* * Give the killed process a good chance to exit before trying * to allocate memory again. -- 1.8.3.1
